Optical fibers are being increasingly utilized for a variety of applications such as data transmission. In order to interconnect the optical fibers, fiber optic connectors are typically mounted upon the end portions of the optical fibers that are to be mated. The optical connections established by mating a pair of fiber optic connectors preferably have relatively low attenuation and a small return loss. In this way such connectors permit the implementation of data transmission at high bandwidths and high transmission capacities over relatively long distances. Moreover, the increasing demand for high transmission capacities leads to optical fibers that are laid in parallel, which in turn require multifiber connectors.
A variety of standardized optical fiber connectors have been developed which are widely used in the industry to interconnect the optical fibers employed in transmission systems. One known type of fiber optic connector is a so-called “MT” type. The MT connector has a connector housing with a front end and a ferrule movably mounted in the housing. The ferrule is biased by a spring to a forward position. When the ferrule is in the forward position, a front face of the ferrule projects from the housing. A multi-fiber cable extends into the housing. The individual fibers of the cable extend through the ferrule to the front face. The front face of the ferrule, and the ends of the fibers, are polished to form a flat surface. The fiber ends are precisely located within the ferrule. The ferrule also has pin-receiving bores. A male MT-type connector has guide pins located in the bores, which project beyond the front face of the ferrule. In a female MT connector the bores remain empty. Two cables may be connected to one another by engaging male and female MT connectors with one another so that the guide pins of the male connector enter the pin receiving bores of the female connector.
While these connectors can provide a good connection between the individual fibers of the two cables with low optical transmission losses, some modern applications are placing increased performance and reliability demands on them. In particular, the connectors must meet Telcordia GR-1435-CORE requirements. For example, Telcordia requirements specify that optical fiber connectors have an insertion loss that does not exceed 0.80 dB. The connector should continue to meet this requirement after being mated and remated 200 times without cleaning after every mating (only cleaning after 25 mates is permitted on one side of the connector and after 50 mates for the other side). The requirement is intended to ensure that the connector does not self generate contamination that may inhibit its performance. Unfortunately, conventional multifiber optical connectors generally do not satisfy this requirement unless the connector is thoroughly cleaned more frequently than the Telcordia requirements.
This insertion loss degradation is particularly problematic when these connectors are employed in optical backplanes. When used in optical backplanes the contaminated connector surfaces are often located within other equipment to which it can be difficult to gain access to clean the contamination from the connector.